In many respects internal gravity waves (GWs) still pose major questions both to the atmospheric sciences and oceanography. Important issues are GW radiation from their various relevant sources, their propagation through and interaction with the larger-scale flow, wave-wave interactions in general, wave breaking and its implications for mixing, and the parameterization of these processes in models not explicitly resolving GWs. Also the observational record, both on a global scale and with respect to local small-scale processes, is not yet sufficiently able to yield appropriate constraints. The session is intended to bring together experts from all fields of geophysical fluid dynamics working on related problems. Presentations on corresponding theoretical, modelling, experimental, and observational work are all welcome.